docs: def is_Linear(self):
          """Returns True if expression is linear (a polynomial with degree 1 or 0) (read-only)."""
          coeff_dict = self.expression.as_coefficients_dict()
          for key in coeff_dict.keys():
              if len(key.free_symbols) < 2 and (key.is_Add or key.is_Mul or key.is_Atom):
                  pass
              else:
                  return False
              if key.is_Pow and key.args[1] != 1:
                  return False
          else:
              return True